混合土物理性质试验研究∗

土体的物理性质与力学性状之间存在一定的联系,研究不同混合比例的混合土的物理性状变化,对于快速测定混合土体的力学参数有很大的帮助.通过对两种原始黏土及人工配制的五种不同混合比例的混合土的物理性质进行研究,探讨混合土的颗粒粒径分布、土粒密度、液限以及塑性指数随混合比例的变化规律.研究结果表明:原始土的性质对混合土体的基本物理性质产生重要的影响.混合土的颗粒粒径分布和土粒密度按混合比例成比例的发生变化,随着混合土中膨润土百分含量的增加,其黏粒含量线性增加,粉粒含量线性减小,砂粒含量线性减小;混合土的液限与塑性指数的变化规律一致,以非线性的方式随着混合土混合比例的变化而变化,其中在混合土中含有膨润土的情况下,这种变化趋势更加明显.     

Effect of NOM characteristics on brominated organics formation by ozonation

In this study, organic fractions, namely, humic acid, fulvic acid, hydrophobic base and neutral, and hydrophilic acid, base, and -neutral, were extracted from source water. First, the characteristics of the organic fractions, such as carboxylic acidity, phenolic acidity, ultraviolet absorbance, and aromatic content, were analyzed. Further, a systematic study was carried out to the by-products obtained when organic fractions, to which various amounts of bromide had been added, were oxidized with ozone. Samples after ozonation were analyzed for several brominated organics. The results indicate that the characteristics of the aquatic organic matter, including carboxylic/phenolic acidity, aromatic/aliphatic content, and ultraviolet absorbance, appear to affect the formation of halogenated organics. In general, hydrophobic organics having higher phenolic acidity, aromatic content, and ultraviolet absorbance have higher ozone consumption and produce higher concentrations of brominated organics than hydrophilic organics. It was also found that humic acid demonstrated the highest bromoform (CHBr(3)), dibromoacetic acid (DBAA), and 2,4-dibromophenol (2,4-DBP) formation, whereas hydrophilic neutral produced less CHBr(3) and 2,4-DBP than the rest of the organic fractions but produced the highest amount of dibromoacetone (DBAC) and dibromoacetonitrile (DBAN).     

重金属汞对海洋底栖动物毛蚶和紫贻贝毒性效应研究

本文基于我国近海典型底栖双壳类生物毛蚶、紫贻贝急性和慢性毒性效应实验数据,分析了重金属汞对受试生物体质量、体长及消化腺超氧化物歧化酶(superoxide dismutase, SOD)酶活力的影响,获取了无观察效应浓度(No Observed Effect Concentration, NOEC),并以生存率为反应终点分析计算了重金属汞的非检测毒性效应浓度及半致死浓度。结果表明,各实验组SOD酶活力的组内方差与组间方差的差异整体上并不显著(P > 0.05),实验周期内仅在个别时间处理组间存在显著性差异(P < 0.05);实验周期内毛蚶和紫贻贝体质量、体长的组内方差与组间方差并没有显著性差异(P > 0.1),体长及体质量不适合作为毒性效应的评价终点。重金属汞对毛蚶、紫贻贝的非检测毒性效应浓度分别为23.7 μg·L-1、87.8 μg·L-1,半致死浓度分别为683.4 μg·L-1、773.2 μg·L-1。     

无定型纳米TiO2吸附去除饮用水中的低浓度As(Ⅲ)

研究了纳米无定型TiO2颗粒对饮用水中低浓度的三价砷As(Ⅲ)吸附行为。纳米TiO2颗粒吸附剂的BET表面积为205 m2/g,计算的BJH吸附平均孔径为4.02 nm(4 V/A)。对起始As(Ⅲ)浓度为150μg/L的模拟含砷水,经过5h的吸附处理后残余浓度不足4μg/L,As(Ⅲ)去除率达到97%。反应起始阶段吸附速率较快,84%的As(Ⅲ)能够在20min内去除。As(Ⅲ)吸附动力学较好地符合拟二级动力学模式。最佳As(Ⅲ)吸附pH为9.3,低于此值,随酸性增加吸附速率有所降低;而高于此值的强碱性pH对吸附有强烈抑制作用。在平衡浓度较低的情形下(10～220μg/L),Lang-muir,Freundlich和Dubinin-Radushkevich(D-R)吸附等温式均可较好拟合吸附行为,但中性和弱碱性条件下更符合Fre-undlich吸附等温式;平衡浓度大于220μg/L,吸附容量随平衡浓度增加而迅速增加,最大吸附容量在低浓度下达到4.79 mg/g。     

EDTAD-modified cassava stalks loaded with Fe3O4: highly efficient removal of Pb2+ and Zn2+ from aqueous solution

Environmental Science and Pollution Research - In this study, a novel magnetic cassava stalk composite (M-EMCS) was prepared through modification with ethylenediamine tetraacetic anhydride (EDTAD)...     

Quantification of the Exposure–Lag–Response Association Between Air Pollution and Respiratory Disease Morbidity in Chongqing City,China

Environmental Modeling & Assessment - The health effects of air pollution on respiratory disease morbidity and mortality commonly vary with air pollutants’ intensity and latency after...     

Response relationships between abrupt seasonal temperature changes/warming (cooling) hiatuses in China and their influencing factors

Environmental Science and Pollution Research - The mechanisms of abrupt seasonal temperature changes and warming (cooling) hiatuses remain unclear. Clarifying how they respond to various...     

应用概率理论拓宽MPN值的计算与实用性

应用多管法检测大肠菌群细菌数是一种适用各种水样的行之有效的检验方法，但此方法操作繁琐，数据处理较难。本文应用概率理论，推导出多种情况下大肠菌群最可能数ＭＰＮ值计算公式，并编制了方便可靠的ＨＢＧ程序，从而进一步提高了此法的实用价值。     

川江流域的土壤退化与防治

川江流域地区土壤退化按肥力因素分类，并以专家系统确定的指标分类统计表明：土壤物理性退化中以水分不调、过砂和板结化较严重；土壤结构性退化中，以土层浅薄化较显著；土壤营养性退化中，以缺硼、钼、磷较突出，成因主要是生态脆弱、土壤侵蚀作用和过渡开发利用，据此提出了防治退化的基本措施。并从持续发展角度提出了适应该区土壤退化特点的持续农业系统。     

长江经济开放开发带湖北科技发展态势及对策

湖北长江经济带的开放开发是在经济发展具有一定实力基础上的再开放再开发，只有以科技为主导，才能使其立足高起点，体现高水平，实现新突破，要始终把握“围绕一条主线，把握两个坚持，努力实现四化”的指导思想，着力建设湖北沿江高新产业带，星火技术密集带，信息公路网络带（一江三带），使湖北长江经济带成为我国中部的科技走廓，为此，要优化科技资源配置，提高研究开发投资水平，建设“八个中心”健全科技服务体系，完善宏观